1. Field of the Invention
The present invention relates to devices for minimizing or eliminating the hazards associated with fuel overflow. More particularly, the present invention relates to minimizing or eliminating fuel spillage associated with filling fuel storage containers including, but not limited to, watercraft fuel tanks.
2. Description of the Prior Art
It is well known to use storage tanks for holding a variety of fluids such as oil, gasoline, and diesel fuel to name a few. Proper filling of storage tanks is a universal concern, as overfilling of storage tanks may result in spillage, damage to the tank or filling equipment, contamination of land or ground water, or other serious and potentially dangerous results. Concerns over spillage of the tank contents are particularly acute when the tank contents are flammable, toxic and/or environmentally hazardous.
Spillage from fuel tanks on watercraft including, but not limited to, pleasure and small commercial fishing boats is particularly troublesome. Some contemporary estimates of such fuel spillage are in excess of six million gallons annually on the waterways of the United States alone. Globally, fuel spillage is many times this amount. The resultant fuel losses are economically and ecologically detrimental in terms of wasted fuel resources and environmental contamination. The problem has led the Environmental Protection Agency to mandate that any such spillage be subject to heavy fines.
The internal fuel tank of a watercraft is typically provided with a vent to enable vapor and fumes to escape under pressure while fuel is being pumped into the fuel tank via the fuel fill tube. As the engine consumes fuel, air is drawn into the tank via the air vent to fill the space from the consumed fuel. Venting is also necessary to accommodate expansion of the fuel when it is heated. During filling of the fuel tank, some fuel may be discharged through the vent into the water as the attendant attempts to fill the tank to capacity. In fact, it is not unknown for filling attendants to purposely fill the tank until fuel is discharged from the vent, using this as an indication that the tank is completely full. It is also possible that fuel may be discharged through the vent subsequent to filling. For example, fuel can be discharged through the vent in a tank filled to capacity as a result of the watercraft listing from side to side due to waves, wind or other causes. Also, fuel will be discharged through the vent in a tank filled to capacity if a subsequent rise in ambient temperature causes the fuel in the tank to expand.
The use of fuel dispensing nozzles that automatically shut off the flow of fuel can aid in avoiding or limiting fuel spillage during filling. The typical automatic shutoff nozzle includes a spout containing a vacuum tube in communication with a venturi near the nozzle handle. The vacuum tube terminates in a pressure sensor port near the exit end of the spout. The venturi is connected to a diaphragm, which diaphragm is coupled to a mechanical device that shuts off fuel flow through the nozzle. In operation, fuel flows through the venturi before passing out of the spout. The passage of fuel through the spout creates a vacuum and air is drawn into the sensor port, through the vacuum tube and into the venturi. An air flow balance is created within the nozzle and the diaphragm remains stationary. When fuel fills the tank and covers the sensor port, the air flow through the vacuum tube stops, a vacuum is created in the venturi by the fuel passing through it. The vacuum buildup in the venturi causes diaphragm movement, which triggers movement of the mechanical device resulting in nozzle shutoff. Unfortunately, automatic fuel shutoff may not occur at the desired time in all situations, including in regard to filling fuel tanks having vent tubes, such as in watercraft.
Specifically in regard to filling the fuel tank of a watercraft, both the fuel fill tube and the vent tube are open to atmospheric pressure and allow air to flow in and out freely during refueling. During the filling process, a turbulent mixture of fuel and air creates foam on the surface of the fuel in the tank. The foam covers the surface of the fuel and rises up into the fuel fill tube and the vent tube as the fuel in the tank rises. When the foam backs up through the fuel fill tube and reaches the sensor port of the fueling nozzle, its viscosity is insufficient at the sensor port to produce the vacuum buildup required in the venturi to trigger automatic nozzle shutoff. As fuel continues to enter the tank, the foaming fuel-air mixture passes into and through either or both of the fuel fill tube and the vent tube to the surrounding environment until such time as enough liquid fuel at the sensor port causes the pressure differential at the venturi required for shutoff.
It can be seen that current filling procedures and devices do not minimize or eliminate fuel overflow through at least the fuel fill tube, and possibly the vent tube, if the nozzle is not shut off manually. Moreover, as noted, discharge through the vent tube may occur even after triggering of automatic shutoff. For example, if the fuel tank is filled to near capacity, fuel can be discharged through the vent tube due to boat listing or fuel expansion.
Many prior approaches to spill prevention or minimization rely on the use of a relatively large reservoir designed to capture overflow. No serious attempt is made to improve the functionality of the automatic shut-off and the system still relies primarily on operator attention. However, the use of a reservoir consumes valuable space on the watercraft and may not address the problems associated with the fuel-air foam mixture when using automatic shutoff nozzles. As the number of automatic shutoff nozzles continues to increase, it is preferable to have an alternative solution for fuel spillage prevention and minimization than a substantial reservoir. Specifically, it would be useful to have a device to minimize or eliminate fuel spillage suitable for use with automatic shutoff nozzles.
Accordingly, there is a need for a device arranged to minimize or eliminate fuel spillage associated with a watercraft fuel tank both during and after filling of a storage tank. It would be desirable to have such a device that is compatible with the use of automatic shutoff fuel nozzles and that does not require provision of a substantial overflow reservoir. Further, it would be desirable to have such a device that is substantially compatible with existing watercraft fueling arrangements.